Filoviruses cause periodic devastating hemorrhagic fever outbreaks in Africa. Because of the high rates of mortality caused by these infections and high transmissibility of these viruses in the human population, this group of viruses has been placed on the Category A select agent list that has been established by the Centers for Disease Control and Prevention. The cellular receptor for Ebola and Marburg virus entry into mammalian cells was identified as folate receptor-a several years ago. Subsequent studies have indicate that folate receptor-a does not serve as the Ebola receptor in airway epithelium or macrophages and these investigations provide evidence that calls the role of the folate receptor-a in entry of filoviruses into question in general. Here we will use two independent approaches to identify cellular receptor(s) for filoviruses: 1) a bioinformatics-based approach and 2) a functional filovirus glycoprotein binding approach. In the first approach, filoviral glycoprotein pseudotyped retroviral constructs will be transduced into a series of well- characterized human tumor lines (NCI60 cells). Viral transduction data will be correlated with the gene expression profiles for these lines to identify transmembrane domain and GPI-linked proteins as potential candidates for filovirus receptors. In preliminary studies using these cell lines, one novel transmembrane domain protein has been identified as a candidate receptor. In parallel, potential viral receptors will be purified through affinity purification approaches. Resulting purified fractions will be tested for their ability to bind to filovirus glycoproteins in virion overlay protein binding assays (VOPBAs). Studies will then be performed to determine if the candidate receptor(s) are necessary and sufficient for Ebola and Marburg glycoprotein dependent entry. Finally, the efficacy of the potential receptor to support filovirus infection will be determined. Identification of cellular receptor(s) that are utilized by filoviruses for in vivo infection is an important step in developing anti-viral agents to these viruses. Identification of the cellular co-receptors for HIV resulted in the development of new drugs that block co-receptor usage. Development of equivalent drugs for the filoviruses might prove to be successful in limiting new outbreaks. [unreadable] [unreadable]